Method and apparatus for cleaning an image transfer member

ABSTRACT

An imaging device comprising an imaging surface on which images are formed; an image transfer surface which receives the images onto an image transfer portion thereof at a first transfer region and from which images are transferred at a second transfer region; and a cleaning arrangement including a cleaning surface which engages the image transfer portion at a cleaning region of the transfer surface. The image transfer portion receives a non-image pattern from the imaging surface at the first transfer region and the cleaning surface collects the non-image pattern at the cleaning region.

RELATED APPLICATIONS

The present application is a US national stage application of PCTapplication PCT/IL96/00173, filed Dec. 3, 1996.

FIELD OF THE INVENTION

The present invention relates to cleaning of image transfer surfaces,particularly the surfaces of image transfer members used in liquid tonerimaging.

BACKGROUND OF THE INVENTION

The use of image transfer members in electrostatic imaging is wellknown. Typically, an intermediate transfer surface is used to transfer atoner image from an imaging surface to a final substrate. This transferis typically aided by heat and pressure.

Various types of intermediate transfer members are known and aredescribed, for example in U.S. Pat. Nos. 3,862,848, 4,684,238, 4,690,539and 4,531,825, the disclosures of all of which are incorporated hereinby reference.

Belt-type intermediate transfer members for use in electrophotographyare known in the art and are described, inter alia, in U.S. Pat. Nos.3,893,761, 4,684,238 and 4,690,539, the disclosures of all of which areincorporated herein by reference.

The use of intermediate transfer members and members including transferblankets for offset ink printing is also well known. Such blankets havecharacteristics which are suitable for ink transfer but are generallynot usable, per se, for liquid toner imaging.

Desirably, the transfer of the toner image from the intermediatetransfer surface onto the final substrate is complete. However, it isappreciated that some residual toner may remain on the surface aftereach transfer. The residual toner typically comprises deformed tonerparticles, some of which may be at least partially fused to otherparticles, which may adhere to the transfer surface and may accumulateto substantial amounts after many imaging cycles. This accumulation ofthe residual toner particles results in non-homogeneous and/or uncleantransfer of the toner images onto the final substrate.

Cleaning of intermediate transfer members is known in the art. To enablecontinuous cleaning while avoiding erasure of the image beingtransferred, the cleaning station in other prior art devices is locateddownstream of the site at which the image is transferred onto the finalsubstrate, prior to the transfer of a subsequent image to theintermediate transfer member.

In other known systems, the intermediate transfer member is periodicallycleaned by printing a series of toner patterns, hereinafter referred toas “non-images”, onto the final substrate. Printing of the non-images isbased on applying a substantially continuous layer of fresh toner ontothe intermediate transfer member and transferring the layer of liquidtoner onto a final substrate, whereby the deformed residual tonerparticles adhere to the fresh toner and are thus removed from theintermediate transfer member. A substantially continuous or continuouslayer of toner on the intermediate transfer member is typically obtainedby developing a substantially continuous non-image on the imagingsurface and transferring the developed non-image onto the intermediatetransfer member.

To economize on the use of liquid toner, the substantially continuousnon-image can be formed of a plurality of screen images each of whichcovers only a predetermined portion of the surface area of theintermediate transfer member. A sequence of such screen images, eachpreferably using a different color toner, provides complete coverage ofthe intermediate transfer member and collects substantially all theresidual toner of all the color toners. It is appreciated that differentcolor toners have different physical properties and, therefore, somecolor toners are more effective, e.g. more adhesive, than others inremoving residual toner particles.

Cleaning of the intermediate transfer member by printing on the finalsubstrate, as described above, generally requires at least eight imagingcycles for each cleaning session. The final substrate bearing theprinted non-images which are formed during the cleaning session cannotbe re-used and is, thus, discarded after the cleaning session,increasing maintenance costs. When the imaging system is designed forprinting on a continuous final substrate as described, for example, inPCT publications WO 96/01442 and 96/31809, each cleaning sessionintroduces a series of undesired non-images between consecutive images,interrupting the sequence of images formed on the final substrate.

SUMMARY OF THE INVENTION

It is an object of some aspects of the present invention to provide amethod and apparatus for cleaning an image transfer surface in imagingapparatus, especially in imaging apparatus using electrostaticallycharged liquid toner.

According to one aspect of the present invention, a cleaning rollerhaving a sticky surface is selectively brought to contact with the imagetransfer surface. A toner pattern, hereinafter also referred to as atoner non-image, is developed on an imaging surface of the imagingapparatus, and is transferred onto the image transfer surface. Residualtoner on the image transfer surface, from previous imaging cycles,adheres to the fresh toner of the non-image. When the cleaning rollerengages the image transfer surface, toner of the non-image istransferred onto the sticky surface of the cleaning roller. Preferably,in this aspect of the present invention, the cleaning roller selectivelyengages the image transfer surface only during predefined cleaningsessions. Therefore, the cleaning roller can be positioned anywherealong the image transfer surface, e.g. upstream of the location at whichimages are transferred onto a final substrate during normal printing.Furthermore, according to this aspect of the present invention, theimage transfer surface does not engage the final substrate during thecleaning sessions.

According to another aspect of the present invention, a cleaning rollerhaving a sticky surface continuously engages the image transfer surface,collecting residual toner particles therefrom. Periodically, apredefined toner non-image is formed on the surface of the intermediatetransfer member and is not transferred onto the final substrate. Thenon-image, which includes fresh liquid toner, is collected by thecleaning roller and a layer of fresh toner is coated onto the surface ofthe roller. Thus, according to this aspect of the present invention,printing of non-images is utilized to renew the stickiness of the stickysurface. Since the cleaning roller continuously engages the imagetransfer surface, the cleaning roller is positioned downstream of thelocation at which images are transferred onto the final substrate.

Under some circumstances, it may be desirable to increase the stickinessof the toner on the roller by heating the roller or by plasticizing thetoner on the roller by wetting it with carrier liquid or with a heavymineral oil having a very low volatility, a high viscosity and a highflash point, such as Marcol 82. However, under normal circumstances,utilizing a heated intermediate transfer member which heats the rollerby conduction, such additional measures are generally unnecessary andmay even result in less optimal operation of the system.

It is appreciated that residual toner from incompletely transferredimages which is transferred onto the cleaning roller accumulatesgradually, over many cleaning sessions, into a thick layer of driedtoner which enlarges the effective diameter of the cleaning roller.Therefore, in preferred embodiments of the present invention, theaccumulated layer of toner is removed periodically from the cleaningroller.

In some preferred embodiments of the present invention, the non-imagesprinted during the cleaning/surface renewal sessions include “sky shot”images, i.e. images which provide a substantially full coverage of theusable area of the intermediate transfer surface. In other preferredembodiments of the present invention, the non-images include predefinedpatterns which do not fully cover the usable area on the image transfersurface but which are sufficiently dense to interact substantially withall the residual toner particles. Additionally or alternatively, thenon-images include a series of complementary patterns which aggregate toprovide a substantially full coverage of the image transfer surface.

In some preferred embodiments of the invention, only an area of theimage transfer surface corresponding to the surface area of the cleaningroller is covered by the non-images, whereby the stickiness of thecleaning surface is renewed with minimal wastage of liquid toner. Therenewed sticky surface efficiently removes residual toner from the imagetransfer surface.

There is thus provided, in accordance with a preferred embodiment of thepresent invention, an imaging device comprising:

an imaging surface on which images, preferably toner images and morepreferably liquid toner images are formed;

an image transfer surface which receives the images at a first transferregion and from which the images are transferred at a second transferregion downstream of the first transfer region; and

a cleaning arrangement which engages said image transfer surface at acleaning region of the image transfer surface situated between the firstand second transfer regions downstream of said first transfer region andupstream of the second transfer region.

Preferably, the cleaning arrangement comprises a cleaning surface whichengages the image transfer surface.

In a preferred embodiment of the invention, the image transfer surfacereceives a non-image pattern, preferably a toner pattern and morepreferably a liquid toner pattern, from said imaging surface at saidfirst image transfer region and wherein said cleaning surface collectssaid non-image pattern at said cleaning region.

There is further provided in a preferred embodiment of the invention animaging device comprising:

an imaging surface on which images, preferably toner images and morepreferably liquid toner images are formed;

an image transfer surface which receives the images at a first transferregion and from which images are transferred at a second transfer regiondownstream of the first transfer region; and

a cleaning arrangement including a cleaning surface which engages saidimage transfer surface at a cleaning region of the transfer surface,

wherein said image transfer surface receives a non-image pattern,preferably a toner pattern and more preferably a liquid toner pattern,from said imaging surface at said first transfer region and wherein saidcleaning surface collects said non-image toner pattern at said cleaningregion.

Preferably, the cleaning region is downstream of the second transferregion and upstream of the first transfer region.

In a preferred embodiment of the invention, the cleaning surfacecontinuously engages the image transfer surface.

In a preferred embodiment of the invention the non-image patterncomprises a pattern which provides substantially full coverage of atleast a portion of the image transfer surface. Preferably, the non-imagepattern comprises a pattern which covers an area on said image transfersurface corresponding to the area of said cleaning surface. Preferablysaid non-image pattern comprises a non-continuous pattern which coverspredetermined portions of the image transfer surface.

In a preferred embodiment of the invention, the cleaning arrangementengages the image transfer surface only during predefined cleaningsessions.

In a preferred embodiment of the invention, the cleaning surfacecomprises a surface of a cleaning roller, preferably one having a stickysurface.

There is further provided, in accordance with a preferred embodiment ofthe invention, a method of cleaning an image transfer surface in animaging device comprising an imaging surface on which images, preferablytoner images and more preferably liquid toner images, are formed and animage transfer surface which receives images at a first transfer regionand from which the images are transferred at a second transfer region,the method comprising:

providing a cleaning member;

intermittently engaging said transfer surface with a cleaning memberbetween said first and second transfer regions downstream of said firsttransfer region.

Preferably the method further comprises:

developing a predefined non-image pattern on said imaging surface; and

transferring said predefined non-image pattern onto said image transfersurface at said first transfer region.

There is further provided in accordance with a preferred embodiment ofthe invention a method of cleaning an image transfer surface in animaging device comprising an imaging surface on which images, preferablytoner images and more preferably liquid toner images, are formed, animage transfer surface which receives images at a first transfer regionand from which the images are transferred at a second transfer regionand a cleaning surface which engages the image transfer surface at acleaning region to remove residual image material remaining on thetransfer surface after transfer of the images therefrom, the methodcomprising:

periodically developing a predefined, non-image, pattern on said imagingsurface; and

transferring said predefined non-image pattern, preferably a tonerpattern and more preferably a liquid toner pattern, onto said imagetransfer surface at said first transfer region and

engaging said image transfer surface with said cleaning member at saidcleaning region.

Preferably, the non-image pattern provides substantially full coverageof at least a portion of the image transfer surface.

Preferably, the non-image pattern comprises a pattern which covers anarea on said image transfer surface corresponding to the area of saidcleaning surface.

In an embodiment of the invention, the toner pattern comprises anon-continuous pattern which covers predetermined portions of the imagetransfer surface.

Preferably, the non-image patter is transferred to the cleaning surface.Preferably, the non-image pattern transferred to the cleaning surfaceacts as a collector of residual image material on the transfer surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a simplified cross-sectional illustration of a portion ofimaging apparatus including an arrangement for cleaning an imagetransfer surface, constructed and operative in accordance with apreferred embodiment of the present invention;

FIG. 2 is a perspective view of the cleaning arrangement of FIG. 1,showing a cleaning roller thereof in a dismounted condition;

FIG. 3 is a partial cross-sectional illustration of the construction ofthe cleaning roller according to a preferred embodiment of theinvention;

FIG. 4 is a knife usable for the removal of toner layers from thecleaning roller, in accordance with a preferred embodiment of theinvention; and

FIG. 5 shows the knife of FIG. 4 in use.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1 which is a simplified cross-sectionalillustration of imaging apparatus including an arrangement 100 forcleaning an image transfer surface 32 of an image transfer member 30,constructed and operative in accordance with a preferred embodiment ofthe present invention. The imaging apparatus includes an imaging surface12, preferably a photoreceptor surface as is known in the art, forexample, as disclosed in U.S. Pat. Nos. 5,376,491 and 5,508,790, thedisclosures of which are incorporated herein by reference, mounted on adrum 10 which is rotated in the direction indicated by an arrow 11.Surface 12 engages image transfer surface 32 at a first transfer region20, where images formed on surface 12 are transferred onto surface 32.Member 30 is rotated in an opposite sense from that of drum 10, asindicated by arrow 31, so as to produce substantially zero relativemotion between surface 12 and surface 32 at first transfer region 20.Image transfer member 30 preferably includes a multi-layered imagetransfer blanket 34 having a release layer 35, as described, for examplein U.S. Pat. Nos. 5,089,856 or 5,047,808 or in PCT Publications WO94/23347 and WO 96/11426, the disclosures of which are incorporatedherein by reference; or other release layers as known in the art.

As is known in the art, member 30 is maintained at a suitable voltageand temperature for electrostatic transfer of a toner image from imagingsurface 12. The toner image is preferably subsequently transferred fromintermediate transfer member 30 onto a final substrate 50, such as apaper or polymer substrate, preferably by heat and pressure, at a secondtransfer region 25. Pressured contact between surface 32 of member 30and substrate 50 at region 25 is preferably provided by an impressionroller 40 which rotates in a direction opposite that of member 30, asindicated by arrow 41. Such second transfer is very well known in theart.

In some preferred embodiments of the present invention, multi-colorimages are produced by sequentially transferring a plurality of singlecolor images, in alignment, onto surface 32 of member 30. A completemulti-color image formed of the plurality of single color images issubsequently transferred, in one action, onto the surface of finalsubstrate 50. In these preferred embodiments of the present invention,substrate 50 is inserted into region 25 and urged against surface 32 byimpression roller 40 only during the transfer of the multi-color image.Between multi-color transfers, intermediate transfer member 30 andimpression roller 40 are disengaged. Alternatively, each single colorimage may be separately transferred to substrate 50 via intermediatetransfer surface 32, as known in the art.

In some preferred embodiments of the present invention, a plurality oftoner images are sequentially printed on a single, continuous, substrate50, as described, for example in PCT publications WO 96/01442 and WO96/31809. In these preferred embodiments of the present invention,substrate 50 is not continuously in contact with image transfer surface32 of member 30, in order to enable repositioning of substrate 50vis-a-vis surface 32 between imaging cycles. As described below,substrate 50 is also disengaged from surface 32 during cleaning and/orsurface renewal sessions in accordance with preferred embodiments of thepresent invention.

As described above, image transfer blanket 34 preferably includesrelease layer 35 which is outermost on the blanket when it is mounted onmember 30. Release layer 35 is preferably about 100 micrometers thickand is preferably formed of a silicone material. Details of a preferredrelease layer 35, including preferred processes of forming releaselayers, are described in the aforementioned PCT publications WO 94/23347and WO 96/11426.

Reference is now made also to FIG. 2 which schematically illustrates aperspective view of a preferred cleaning arrangement 100, showing acleaning roller 105 thereof in a dismounted condition. As shown in FIGS.1 and 2, cleaning arrangement 100 includes carrier arms 104 havingfork-shaped bottom ends 111 which are supported on pivot axles 110, suchthat arms 104 are pivotable about axles 110. Arms 104 are substantiallyparallel and are preferably supported by connecting bars 120. Cleaningroller 105 is mounted between parallel arms 104 using bearings 116 whichenable free rotation of roller 105 about its longitudinal axis. Axles110 are preferably fixedly mounted to a support structure of the imagingapparatus.

Roller 105 (shown in greater detail in FIG. 3) preferably includes aninner, preferably metal, core 102 covered with layer 114 of a relativelysoft resilient material such as polyurethane. Preferably, the layer hasa thickness of 25-35 micrometers at the center of the roller and a ShoreA hardness of 20-25. Layer 114 is thinner at the ends of the roller inorder to provide higher pressure thereat to aid in removing toner whichtends to accumulate along the edges of the intermediate transfer member.It should be clear that thicker or thinner layers and/or harder orsofter material may be used for layer 114 depending, inter alia, on thecharacteristics of the intermediate transfer member, the toner and thetemperature of the roller. Layer 114 has been found to be sufficientlysticky to toner on surface 32 of member 30 to enable efficientcollection of residual toner, as described, in detail, below.

In a preferred embodiment of the invention, as shown in FIGS. 1 and 2,upper portions 124 of arms 104 are connected, via connectors 108, torespective pistons 126 of actuators 106, which preferably includeair-pressure actuators. When air pressure is supplied to actuators 106,via air-pressure inlet 122, pistons 126 move towards image transfermember 30 pushing connectors 108 which, in turn, push upper portions 124of arms 104. This results in forceful motion of cleaning roller 105towards member 30, urging the surface of layer 114 of roller 105 againstimage transfer surface 32. When the supply of air-pressure to actuators106 is deactivated, springs 107 in actuators 106 push pistons 126 awayfrom member 30, causing disengagement between roller 105 and surface 32.In a preferred embodiment of the invention, the supply of air-pressureto actuators 106 is selectively activated, to produce selectiveengagement between roller 105 and intermediate transfer member 30 onlyduring cleaning and/or surface renewal sessions as described below. Asfurther shown in FIGS. 1 and 2, actuators 106 are preferably fixedlymounted on a support rod 118 which is fixedly mounted to the supportstructure of the imaging apparatus.

It should be appreciated that air-pressure actuators 106 may be replacedby any suitable means known in the art for producing selectiveengagement between cleaning roller 105 and intermediate transfer surface32. For example, hydraulic actuators or any other type of actuators maybe used in place of actuators 106.

In accordance with preferred aspects of the present invention, stickysurface 114 is selectively brought to contact with the image transfersurface only during predefined cleaning sessions. At the beginning ofeach cleaning session, a liquid toner pattern, hereinafter referred toas a toner non-image, is developed on imaging surface 12, and istransferred onto surface 32 of member 30 as is known in the art. Thenon-image developed on surface 12 may be a “sky shot” image, i.e. animage which provides a substantially full coverage of the operative areaof intermediate transfer surface 32.

Alternatively, the non-image developed on surface 12 includes apredefined pattern which does not fully cover the operative area of theimage transfer surface but which is sufficiently dense to interactsubstantially with all residual toner on surface 32, as described below.Such a non-image is referred to herein as having “substantially fullcoverage.” In some preferred embodiments of the invention, a series ofcomplementary patterns are sequentially transferred onto the imagetransfer surface, which patterns aggregate to provide at least asubstantially full coverage of at least a portion of the image transfersurface.

It should be appreciated that residual, typically deformed and generallypartially fused, toner particles, accumulated over imaging cycles priorto the cleaning session, adhere to the toner non-image on image transfersurface 32. When the sticky surface of cleaning roller 105 engagessurface 32, the toner non-image is removed from the image transfersurface together with the residual toner particles. Furthermore, thefresh toner transferred onto roller 105 during the cleaning sessionenhances the stickiness of its surface and, thus, further engagementbetween surface of roller 105 and surface 32, without adding additionaltoner, may be utilized to remove additional toner particles from surface32.

In some preferred embodiments of the present invention, only an area ofimage transfer surface 32 corresponding to the area of layer 114 iscovered by the non-images, whereby the stickiness of the cleaningsurface is renewed with minimal wastage of liquid toner. The renewedsticky surface efficiently removes residual toner from the imagetransfer surface.

Since cleaning roller 105 preferably engages surface 32 only during thecleaning sessions, the cleaning roller can be positioned anywhere alongthe image transfer surface, e.g. along the portion of surface 32downstream of first image transfer region 20 and upstream of secondimage transfer region 25, as shown in FIG. 1.

It is appreciated that the toner transferred onto layer 114 of cleaningroller 105 accumulates gradually, over many cleaning sessions, into athick layer of dried toner which enlarges the effective diameter ofcleaning roller 105. Therefore, in preferred embodiments of the presentinvention, the accumulated layer of toner is removed periodically fromthe cleaning roller. To remove the accumulated toner layer from layer114, roller 105 is preferably dismounted, as shown in FIG. 2, and asharp knife or other tool is used to cut through the layer of driedtoner which may, then, be peeled off layer 114. Alternatively, roller105 may be periodically replaced.

FIGS. 4 and 5 respectively show a preferred embodiment of a knife 150suitable for removing a toner layer 160 without damaging layer 114 andan illustration of the knife performing this function. Knife 150includes a handle 152, a lifter portion 154 mounted at one end of the ofthe handle and a knife blade 156 situated to cut toner layer 160 whichis lifted by lifter portion 154. The lifting and cutting process isillustrated in FIG. 5.

In a preferred embodiment of the present invention, the followingcleaning sequence is used for each cleaning session. First, at least one“dry run” is performed, whereby cleaning roller 105 engages surface 32but toner is not applied to surface 32. At this stage, some of theexcess liquid on roller 105 is evaporated and less deformed tonerparticles are collected onto its surface. Then, at least one non-imageas described is transferred onto surface 32. The fresh liquid toner ofthe non-image collects the residual toner and is coated onto layer 114as described above. Finally, at least one additional “dry run” isperformed to ensure maximal removal of the residual toner.

In accordance with other preferred aspects of the present invention, thesticky surface of cleaning roller 105 continuously engages imagetransfer surface 32, collecting residual toner particles therefrom. Itis appreciated, however, that the residual toner, which is typically dryand deformed, degrades the stickiness of the surface. Therefore,according to these aspects of the present invention, a toner non-imageas described above is periodically transferred onto the surface of theintermediate transfer member to renew the stickiness of the surface ofroller 105. The non-image, which includes fresh liquid toner, iscollected by cleaning roller 105 and a layer of fresh toner is coatedonto layer 114. As described above, the renewed surface efficientlyremoves residual toner particles from surface 32. Since, in theseaspects of the invention, cleaning roller 105 continuously engages theimage transfer surface, the cleaning roller must be positioneddownstream of second transfer region 25, contrary to the non-continuousembodiment shown in FIG. 1, which may be positioned anywhere on theintermediate transfer member.

In those systems where a plurality of toner images are accumulated onthe transfer member prior to transfer therefrom, the roller must bedisengaged from the transfer member while the images are beingaccumulated.

It should be understood that some aspects of the invention are notlimited to the specific type of image forming system used and someaspects of the present invention are also useful with any suitableimaging system which forms a liquid toner image on an image formingsurface and, for some aspects of the invention, with powder tonersystems. Some aspects of the invention are also useful in systems suchas those using other types of intermediate transfer members such as beltor continuous coated drum type transfer members. Some aspects of theinvention are suitable for use with offset printing systems. Thespecific details given above for the image forming system are includedas part of a best mode of carrying out the invention; however, manyaspects of the invention are applicable to a wide range of systems asare known in the art for electrophotographic and offset printing andcopying.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by the description and example providedhereinabove. Rather, the scope of this invention is defined only by theclaims which follow:

Claims:
 1. An imaging device comprising: an imaging surface on whichimages are formed; an image transfer surface which receives the imagesonto an image transfer portion thereof at a first transfer region andfrom which images are transferred at a second transfer region; and acleaning arrangement including a cleaning surface which engages saidimage transfer portion at a cleaning region of the transfer portion,wherein said image transfer portion receives a non-image pattern fromsaid imaging surface at said first transfer region and wherein saidcleaning surface collects said non-image pattern at said cleaningregion.
 2. An imaging device according to claim 1 wherein the cleaningsurface is positioned to engage the image transfer portion after theimage transfer portion passes the second transfer region and before itreturns to the first transfer region.
 3. An imaging device according toclaim 1 wherein the cleaning surface continuously engages the imagetransfer surface.
 4. An imaging device according to claim 1 wherein thenon-image pattern comprises a pattern which provides substantially fullcoverage of at least a portion of the image transfer region.
 5. Animaging device according to claim 4 wherein said non-image patterncomprises a pattern which covers an area on said image transfer surfacecorresponding to the area of said cleaning surface.
 6. An imaging deviceaccording to claim 1 wherein said non-image pattern comprises anon-continuous pattern which covers predetermined portions of the imagetransfer portion.
 7. An imaging device according to claim 1 wherein saidnon-image pattern comprises toner particles.
 8. An imaging deviceaccording to claim 7 wherein the non-image pattern is formed of a liquidtoner comprising said toner particles and a carrier liquid.
 9. Animaging device according to claim 1 wherein the cleaning arrangementengages the image transfer surface only during predefined cleaningsessions.
 10. An imaging device according to claim 1 wherein saidcleaning surface comprises a surface of a cleaning roller.
 11. Animaging device according to claim 1 wherein the cleaning surfacecomprises a sticky surface.
 12. An imaging device according to claim 1wherein the images are toner images.
 13. An imaging device according toclaim 12 wherein the images are formed of a liquid toner comprisingtoner particles and a carrier liquid.
 14. A method of cleaning an imagetransfer surface in an imaging device comprising an imaging surface onwhich images are formed, an image transfer surface having an imagetransfer region thereon, which region receives images at a firsttransfer region and from which the images are transferred at a secondtransfer region and a cleaning member having a cleaning surface whichengages the image transfer region at a cleaning region to removeresidual image material remaining on the transfer surface after transferof the images therefrom, the method comprising: periodically developinga predefined, non-image, pattern on said imaging surface; andtransferring said predefined non-image pattern onto said image transferregion at said first transfer region and engaging said image transfersurface with said cleaning member at said cleaning region.
 15. A methodto claim 14 wherein the non-image pattern provides substantially fullcoverage of at least a portion of the image transfer region.
 16. Amethod according to claim 15 wherein non-image pattern comprises apattern which covers an area on said image transfer region correspondingto the area of said cleaning surface.
 17. A method according to claim 14wherein said non-image pattern comprises a non-continuous pattern whichcovers predetermined portions of the image transfer region.
 18. A methodaccording to claim 14 wherein the pattern comprises toner particles. 19.A method according to claim 18 wherein the pattern is formed of a liquidtoner comprising said toner particles and a carrier liquid.
 20. A methodaccording to claim 14 and including, transferring the non-image patternto the cleaning surface.
 21. A method according to claim 20 wherein thenon-image pattern transferred to the cleaning surface acts as acollector of residual image material on the transfer region.
 22. Amethod according to any of claims 14-21 wherein the images are tonerimages.
 23. A method according to claim 22 wherein the images are liquidtoner images comprising toner particles and a carrier liquid.
 24. Animaging device according to claim 1 wherein the cleaning surface ispositioned to engage the image transfer portion after the image transferportion passes the first transfer region and before it reaches the firsttransfer region.
 25. An imaging device according to claim 24 wherein thecleaning surface contacts the image transfer portion when said non-imagepattern is printed and does not contact the surface when an image isprinted.